Buggy code:
public class CSVPersonSerializer extends PersonSerializer { private HDFSCSVWriter [ ] writers ; private enum FileNames { PERSON ( "person" ) , PERSON_SPEAKS_LANGUAGE ( "person_speaks_language" ) , PERSON_HAS_EMAIL ( "person_email_emailaddress" ) , PERSON_LOCATED_IN_PLACE ( "person_isLocatedIn_place" ) , PERSON_HAS_INTEREST_TAG ( "person_hasInterest_tag" ) , PERSON_WORK_AT ( "person_workAt_organisation" ) , PERSON_STUDY_AT ( "person_studyAt_organisation" ) , PERSON_KNOWS_PERSON ( "person_knows_person" ) ; private final String name ; private FileNames ( String name ) { } public String toString ( ) { } } public CSVPersonSerializer ( ) { } public void initialize ( Configuration conf , int reducerId ) { int numFiles = CSVPersonSerializer . FileNames . values ( ) . length ; writers = new HDFSCSVWriter [ numFiles ] ; for ( int i = 0 ; i < numFiles ; ++ i ) { writers [ i ] = new HDFSCSVWriter ( conf . get ( "ldbc.snb.datagen.serializer.socialNetworkDir" ) , ( ( ( CSVPersonSerializer . FileNames . values ( ) [ i ] . toString ( ) ) + "_" ) + reducerId ) , conf . getInt ( "ldbc.snb.datagen.numPartitions" , 1 ) , conf . getBoolean ( "ldbc.snb.datagen.serializer.compressed" , false ) , "|" ) ; } ArrayList < String > arguments = new ArrayList < String > ( ) ; arguments . add ( "id" ) ; arguments . add ( "firstName" ) ; arguments . add ( "lastName" ) ; arguments . add ( "gender" ) ; arguments . add ( "birthday" ) ; arguments . add ( "creationDate" ) ; arguments . add ( "locationIP" ) ; arguments . add ( "browserUsed" ) ; writers [ CSVPersonSerializer . FileNames . PERSON . ordinal ( ) ] . writeEntry ( arguments ) ; arguments . clear ( ) ; arguments . add ( "Person.id" ) ; arguments . add ( "language" ) ; writers [ CSVPersonSerializer . FileNames . PERSON_SPEAKS_LANGUAGE . ordinal ( ) ] . writeEntry ( arguments ) ; arguments . clear ( ) ; arguments . add ( "Person.id" ) ; arguments . add ( "email" ) ; writers [ CSVPersonSerializer . FileNames . PERSON_HAS_EMAIL . ordinal ( ) ] . writeEntry ( arguments ) ; arguments . clear ( ) ; arguments . add ( "Person.id" ) ; arguments . add ( "Place.id" ) ; writers [ CSVPersonSerializer . FileNames . PERSON_LOCATED_IN_PLACE . ordinal ( ) ] . writeEntry ( arguments ) ; arguments . clear ( ) ; arguments . add ( "Person.id" ) ; arguments . add ( "Tag.id" ) ; writers [ CSVPersonSerializer . FileNames . PERSON_HAS_INTEREST_TAG . ordinal ( ) ] . writeEntry ( arguments ) ; arguments . clear ( ) ; arguments . add ( "Person.id" ) ; arguments . add ( "Organisation.id" ) ; <START_BUG> arguments . add ( "workFrom.id" ) ; <END_BUG> writers [ CSVPersonSerializer . FileNames . PERSON_WORK_AT . ordinal ( ) ] . writeEntry ( arguments ) ; arguments . clear ( ) ; arguments . add ( "Person.id" ) ; arguments . add ( "Organisation.id" ) ; arguments . add ( "classYear" ) ; writers [ CSVPersonSerializer . FileNames . PERSON_STUDY_AT . ordinal ( ) ] . writeEntry ( arguments ) ; arguments . clear ( ) ; arguments . add ( "Person.id" ) ; arguments . add ( "Person.id" ) ; arguments . add ( "creationDate" ) ; writers [ CSVPersonSerializer . FileNames . PERSON_KNOWS_PERSON . ordinal ( ) ] . writeEntry ( arguments ) ; } @ Override public void close ( ) { } @ Override protected void serialize ( Person p ) { } @ Override protected void serialize ( StudyAt studyAt ) { } @ Override protected void serialize ( WorkAt workAt ) { } protected void serialize ( Knows knows ) { } }

Fix:
arguments . add ( "workFrom" ) ;